Filter fabric and method of making same



y 11. 1954 .D. c. GERBER 2,677,869

FILTER FABRIC AND METHOD OF MAKING SAME Original Filed Sept. 5, 1947 zzvmvrom DALE C. GERBER BY ATTORNEY Patented May 11, 1954 2,677,369 FILTER FABRIC ANSIZmNIIETHOD or MAKING Dale 0. Gerber, North Canton,

The Hoover Company,

corporation of Ohio Ohio, assignor to North Canton, Ohio, a

Original application September 3, 1947, Serial No.

771,967. Divided an 1951, Serial No. 224,174

8 Claims. (Cl. 26-3) This application is a division of my copending application for Letters Patent, Serial No. 771,967, filed September 3, 1947, which is now Patent No. 2,576,717 directed to a suction cleaner filter.

The present invention relates to filters and more particularly to filters composed of fibrous material having exterior fibers removed.

In the usual filter for suction cleaners the material has a matted napped surface to which the dirt adheres and prevents removal of the dirt when the filter is cleaned, and as a result when the filter is re-used the back pressure becomes excessive and reduces the cleaning efiiciency of the suction cleaner. The present invention provides a filter fabric wherein the matted napped surface is removed to form a smooth surface upon which the dirt initially contacts, and the smooth surface functions to cause the easy removal of the dirt deposited thereon when the filter is cleaned. Removal of the matted napped surface does not injure the fibers in the body portion of the filter material and thus the filtering efiiciency of the material is not reduced.

An object of the invention is to provide a filter formed from fibrous material. Another object is to provide a fibrous filter having projecting fibers shortened while retaining the necessary filtering characteristics. A further object is to provide a fibrous filter adapted for use with a suction cleaner and having the fibers in the dirt contacting surface shortened to form a smooth dirt collecting surface which can be easily cleaned. Another object is to provide a method and apparatus for shortening fibers projecting from the body of a fibrous filter material. Still another object is to provide a method and apparatus for treating fibrous filtering material by subjecting the material to an electrical charge to raise fibers from the body of the material and thereafter shortening the fibers by singeing the latter to substantially the body of the material. Other objects and advantages of the invention will be apparent from the following specification and drawings, wherein:

Figure 1 illustrates the filter in a suction cleaner;

Figure 2 is a view of the apparatus for creating an electrical charge in the filter material to raise the fibers and to singe the projecting fibers;

Figure 3 is a section of the filter material prior to shortening the fibers; and

Figure 4 is a section of the filter material after the fibers have been shortened on the dirt contacting surface of the filter.

The invention herein disclosed is for purposes d this application May 2,

of illustration applied to a suction cleaner comprising a casing it supported on runners l I and having a suction end cap [2 and an exhaust end cap H3. The end cap i2 is provided with an inlet l 4 for connection to an unshown hose and cleaning tool which engages a surface to be cleaned, and the rear end cap l3 has an outlet [5 which can also be provided with a cleaning tool in a manner well known in the art. A dirt filtering bag It is supported in the casing It to remove the dirt from the dirt-laden air passing through the inlet M into the bag, and a motor-fan unit I! provides the suction for moving the air stream and exhausting it through the outlet I 5. The filter material may be paper, cloth or other suitable material and as shown in Figure 3 prior to being processed is a single ply cloth 20 having yarns 2! secured together by Warp face yarns 22, 23, and 24. The exposed surfaces 38 and 3! of the material prior to being processed is a mass of intermingled matted fibers or nap 32, and it is these fibers which retain the dirt in the usual suction cleaner bag and prevent removing all of the dirt when the bag is being cleaned.

The process for removing the matted fibers 01' nap 32 from the surface 30 and comprises a bolt of the material 20 rotatably supported on a shaft 35, and the material is wound onto a shaft 36 by moving the material in the direction of the arrow 31. The material passes through an electrostatic field formed by two electrodes 4c and 4t disposed on opposite sides of the material, and the electrodes are connected to a suitable source of high frequency current. Disposed above the electrode til and beneath the material 20 is a gas manifold 42 having two rows of burners 4343 in the electrostatic field and adjacent the outer fibers of the material.

Movement of the material between the electrodes 46 and 4! causes the material to pass through the electrostatic field and the fibers receive an electrical charge and are aligned with the electric field, and as a result of such charge the nap or fibers are pulled away from and are perpendicular to the body of the material. While the fibers are raised from the body of the material, the burners 63-43 singe the ends of the fibers to shorten the latter and thus prevent the fibers from forming a matted surface, and the resulting surface shown at 45 in Figure 4 provides a relatively smooth dirt contacting surface from which the dirt may easilyibe removed when the filter is being cleaned.

The speed of movement of the material beis shown in Figure 2 tween the electrodes 48 and 4! depends upon the size of the electrodes, the strength of the electrostatic field and the heat of the singeing flame. I have found that the voltage applied to the electrodes can be varied over a wide range and have employed voltages from 1589 to 4900 per square inch. If desired the burners it can be arranged to one side of the electrodes 4e and M.

The processed filter material shown in Figure 4:

is formed into the dirt filtering bag l6. with the smooth surface forming the interior and the napped surface iii the exterior of the bag. The.

dirt-laden air passes through the inlet Hi into the bag it and first contacts the smooth inner surface 45, and the remaining portion of the filter body removes the dirt from the dirt-laden air stream as the latter passes through the material, and the cleaned air is then discharged through the outlet l5.

In cleaning the bag it, the end cap 14 and the bag it removed and the dirt is easily dislodged from the bag because of the relatively smooth inner surface Q5.

While I have shown and described but a single modification of my invention, it is to be understood that this modification is to be taken as illustrative only and not in a limiting sense. I do not wish to be limited to the particular structure and process shown and described, but to include all equivalent variations thereof except as limited by the scope of the claims.

I claim:

1. The method of shortening fibers in fibrous material which comprises applying an electrical charge to the material to raise fibers from the body of the material, and shortening the projecting fibers while charged to substantially the body of the material by a flame independent of said electrical charge.

2. The method of shortening fibers in fibrous material which comprises passing the material through an electric field to raise fibers from the body of the material, and shortening the projecting fibers while in said electric fieldto substantially the body of the material by a flame independent of said field.

3. The method of shortening fibers in fibrous material which comprises applying a highfrequency current to the material to raise fibers from the body of the material, and shortening the projecting fibers in the high frequency current to substantially the body of the material by a fiame independent of said high frequency current.

4. The method of treating a fibrous material for use as a dust filter which comprises passing the material through an electric field to raise fibers from the body of the material, and applying'separate' heat'to the projecting fibers while in said electrical field to shorten the projecting fibersto substantially the body of the material.

5. The method of treating a fibrous material for use as a=dustfilter for suction cleaners which comprises raising fibers along one side of the body'of the material by electrical means, and applying separate heat to the projecting fibers along said one side to shorten the fibers to substantially the body of the material.

6. Apparatus for shortening fibers in a fibrous material, comprising electrodes to create an electrical field for-the material to raise the fibers fromthe body of the material, and means in the electrical field independent of the latter to singe the raised fibers. to shorten the latter.

7. Apparatus for, shortening fibers in a fibrous material, comprising electrodes arranged on opposite sides ofthe material to create an electrical fieldto.v raise thefibersfrom the body of the material, and singeing means independent of said electrodes disposed between one of said electrodes andthe-adjacent. side of saidmaterial to singe the raised fibers to. shorten the latter on said one side. of. said .material...

8..The .method. of shortening fibers in fibrous material which comprises, moving the material between. electrodes to raise-andproject the fibers from. the body of the. material, and shortening the. projected.fibers-independent of said electrodes to. substantially the .body of the material while moving the-latter between said electrodes.

References. Citedin the file of .thispatent UNITED STATES PATENTS Number Name Date 1,726,678 Osthofi Sept. 3, 1929 2,385,873 Melton Oct. 2, 1945 

